The development by Kansas State University agronomists of a wheat variety called Arkan, which looks like a soft wheat but bakes and mills like a hard wheat, has spurred interest in developing an objective means of delineating hard from soft wheat. The present method of classification used by the Federal Grain Inspection Service (FGIS) is visual, based on shape and color characteristics of traditional hard and soft wheats. Plant breeders have traditionally found that the shape and color characteristics that denote a hard wheat tend to be genetically transferred with the end use characteristics of baking, hardness, and milling that constitute hard wheat. However, as cross-breeding between hard and soft wheat continues the two sets of traits do not necessarily transfer together. The result is hard wheats that look like soft wheats and soft wheats that look like hard wheats. Because some of these new varieties have desirable insect resistance, drought resistance, or yield potential, it is imperative that a rapid method be developed to delineate hard from soft wheat based on end-use characteristics rather than on visual characteristics.
Bulk testing methods such as time to grind, resistance to grinding, particle size index and near infrared reflectance can be used to delineate hard from soft samples but are not sensitive enough to identify the degree of adulteration in blended samples. Federal regulations allow a maximum of 5% adulteration of a wheat class with other wheat classes. Beyond the 5% level the end use quality of the wheat is affected.
Our approach to the problem is to measure the hardness of individual kernels within a bulk sample. By measuring a large enough number of individual kernels a good estimation on the level of adulteration can be achieved. This approach has also been chosen by Lai, et al (1985), Determination of Hardness in Wheat Mixtures., working on the problem at the USDA Grain Marketing Research Laboratory in Manhattan, Kans. They developed an instrument which singularizes the wheat kernels and crushes them with a rounded probe at the rate of 15 kernels per minute. They investigated six parameters of the breakage event to determine which parameter gave best delineation between hard and soft wheat. They determined the ratio of the first valley to the first peak on the breakage event curve gave the best separation between hard and soft wheat. Tested using samples of known adulteration levels, the instrument was 90% accurate in determining the level of adulteration.